(1) Field of the Invention
This invention relates generally to display systems, and more particularly to a system and a method to adjust colors to be displayed before writing it into a display RAM.
(2) Description of the Prior Art
The colors of digital images have to be normally adjusted to accommodate to the display system used to display said digital images. Without any adjustment a viewer of digital images will not be satisfied with the colors shown. All display systems such as e.g. color super twist nematic (CSTN), thin film transistor (TFT), organic light emitting diode (OLED), or double layer supertwist nematic (DSTN) displays have their specific flaws in displaying colors. Therefore the colors of digital images have to be adjusted to satisfy the expectations of the viewers of said images.
There is a multitude of methods known to perform said color adjustment.
U.S. Pat. No. 6,262,817 (to Sato et al.) describes a color image system for adjusting colors of inputted images including a color adjusting unit and color display unit. The color display unit simultaneously displays the original image, the adjusted image, and color information for both the original image and adjusted image. A color adjustment matrix is created by the color-adjusting unit based upon color directions inputted to the color display unit with respect to the color information of the original color image. The color adjustment matrix is used to directly adjust the original image without converting the image to a second color space. A color-adjusting unit produces a color adjustment matrix by adding color adjustment direction of the luminance, chroma, and hue, directed by the image display unit used, for the original matrix. After the color adjustment matrix being produced, the adjusted pixel can be produced by calculating the original pixel and the color adjustment matrix.
U.S. Pat. No. 6,388,648 (to Clifton et al.) discloses an LCD projection unit employing a luminance and color balance system employing an LCD array characterization lookup table storing multiple sets of luminance and gamma correction values that are user selectable to control luminance and color balance. The lookup table values are determined by measuring the transfer function of the LCD array in the projection unit for each of a set of red (“R”), green (“G”), and blue (“B”) input data values, converting the resulting S-curve responses to corresponding sets of gamma responses and scaling the gamma responses to generate multiple R, G, and B families of luminance and gamma corrected values. Color balance is adjusted by selecting the particular R, G, and B families of luminance and gamma corrected values that cause the LCD projection unit to match a predetermined ratio of R, G, and B luminance values. Luminance is adjusted by selecting sets of families of R, G, and B, luminance values that maintain the color balance ratio while causing the LCD to transmit the desired overall luminance. The primary colors are adjusted by a method of color mixing implemented by a mathematical matrix algorithm that generates color modification coefficients for a color space conversion circuit. The primary color matching algorithm involves measuring the intrinsic colors coordinates of the primaries, determining a set of predetermined target coordinates, and performing matrix operations to calculate the coefficients used in the color space conversion circuit to convert the measured to the target coordinates, thereby matching the primary colors. When the primary colors are matched, the above-described color balance and luminance matching system adjusts the white and gray balance to result in a well-matched multiscreen display system.
U.S. Pat. No. 4,409,614 (to Eichler et al.) discloses a method wherein color scanning signals generated by scanning the original image are first converted into three primary color signals having actual color values in a predetermined color coordinate system corresponding substantially identically to theoretical color values of the original. It is only after this conversion that the primary signals or signals derived from these signals are converted to another color rendition system, or the gradation is altered, or the color rendition of individual colors in the overall image or in discrete areas is altered, or any other non-linear processing takes place.